1. Field of the Invention
The present invention relates to an endoscope distal hood component provided at an insertion portion distal end of an endoscope in order to ensure a closest approach distance between the insertion portion distal end of the endoscope and a subject.
2. Description of the Related Art
An example of conventional endoscope apparatuses used for surgery is formed to be provided with an observational optical system, a light guide, an air and water feed hole and a suction hole at the distal end of the insertion portion of the endoscope.
With respect to such an endoscope apparatus, illumination light is applied to a subject, e.g., living body tissue, from a light guide, and operations, e.g., suction of air, water, or other substance fed from the air and water feed hole with the suction hole, are performed while the reflected light from the subject is visually identified through an objective lens.
On the other hand, with respect to some endoscopes, a hood component is provided at an insertion portion distal end of the endoscope in order to ensure a closest approach distance between an observation window of an observational optical system and a subject. For example, Japanese Examined Utility Model Registration Application Publication No. 59-15605 discloses a hood component which is freely detachably provided at a distal end of an insertion portion of an endoscope and which is formed into the shape of a substantially regular cylinder.
According to the technology disclosed in this publication, the hood component is fitted to the insertion portion distal end of the endoscope, the endoscope observation is performed while the distal end of the hood component is in contact with the subject and, thereby, the distance between the subject and the end surface of the distal end at which a first lens surface of the objective optical system is located can be maintained constant, so that the observation of an easy-to-move subject, e.g., a mucosa, can be easily performed.
Japanese Unexamined Patent Application Publication No. 2001-224550 discloses a technology in which a substantially cylindrical hood component provided at an insertion portion distal end of an endoscope is formed into the shape not included within the range of the observational field of view.